Fisch EEG Primer Chapter 6 Flashcards

EEG Artifacts

1
Q

Physiologic Artifacts can be divided into two categories:

A
  • Movements

- Bioelectrical Potentials

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2
Q

Non-physiological Artifacts arise primarily from two sources:

A
  • External electrical interference

- internal electrical malfunctioning

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3
Q

A medium to high amplitude potential that only occurs at ONE ELECTRODE is…

A

artifact until proven otherwise

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4
Q

Rythmical/Simultaneous waveforms that appear in unrelated head regions are likely…

A

artifact since evolving electrographic seizures spread to adjacent leads and do not “jump”

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5
Q

Blinking artifact and other eye movements causes the most prominent changes in which leads…

A

vertical eye movments Fp1/Fp2 and horizontal movments in F7/F8 - downward deflections are typically noted as the positively charged cornea causes input 1 to be relatively positive compared with input 2

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6
Q

Describe a lateral rectus spike…

A

On occasion, prior to lateral eye movements, a preceeding single sharp muscle spike may be seen. - this may mimic abnormal epileptiform activity

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7
Q

Eye movement artifacts should be most/least prominent in which distributions

A

More promonent frontally and less prominent posteriorly - increased amplitude posteriorly should raise a “red flag” for alternative explanation

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8
Q

What are some causes of asymmetric eye movement? (4)

A
  • decreased movement of one eye
  • absence or destruction of an eye
  • asymmetric electrode placement
  • frontal skull defect ((lower in amplitude ipsilateral to defect)
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9
Q

Muscle artifact differ from cerebral spike discharges in that…

A

muscle artifacts tends to be of decreased duration

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10
Q

Reducing high frequency filter setting for high frequency muscle artifact my complicate the recording because…

A

changes the form of the waves so that a single potential may have the appearance of a a spike

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11
Q

heart beat artifact can often beating eliminated by…

A

combining ear leads or a balanced neck/chest reference montage

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12
Q

Pulse wave artifact is caused by…

A

temporary changes in electrical contact as pulse wave travels past electrode. Typically frontal/temporal distribution millisec following ECG tracing.

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13
Q

Perspiration artifact consists of…

A

slow waveforms (usually greater than 2 sec in duration) - perspiration changes impedence contact between skin and recording electrode AND slowly changing potentials generated at the sweat glands.

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14
Q

How can perspiration artifact be reduced..

A

cooling the patient and drying the scalp with fan or alcohol

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15
Q

Sympathetic skin response (SSR) also known as the galvanic skin response consists of…

A

slow waves 0.5-1 sec that last 1.5-2 sec with 1-3 prominent phases. Represents an autonomic response medicated by cholinergic neurons in response to sensory or psychic stimulus.

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16
Q

What distribution is the sympathetic skin response typically found?

A

frontocentral channels in longitudinal bipolar montages and a characteristic triple phase reversal in transverse bipolar montages - best monitored by un-abraded palmar and dorsum of hand recording.

17
Q

Movement of the tongue (glossokinetic) and other oropharyngeal structures may result in…

A

wide spread slow waves of maximal distribution in longitudinal bipolar montages in middle of head

18
Q

Palatal myoclonus generally causes…

A

rythmical muscle artifacts at about 60-120/min seen only in referential montages and persist in sleep - appears as fast paired deflections.

19
Q

Tongue movement artfacts can be identified on routine EEG by asking the patient to repeat..>

A

“Lilt”, “TomThumb”

20
Q

Dental restorations WITH dissimilar metals may cause what types of artifact

A

may cause artifacts when metal touches commonly caused by speaking or chewing.

21
Q

Two common types of interference are from…

A

electrostatic (e.g. unshielded power cables) and electromagnetic (e.g. large flow going through cables or transformers)